I'm writing to ask you to support me and my cause/project/etc.. Just a small donation of amount can help me accomplish task/reach a goal/etc.. Your donation will go toward describe exactly what the contribution will be used for. When possible, add a personal connection to tie the donor to the cause.
Most mortgage providers will have a template that you can follow, but in general, your gift letter should include: The donor's name, address and phone number. The donor's relationship to the client. The dollar amount of the gift. The date when the funds were (or will be) transferred.